Monday, December 5, 2016

All About Candles

Candles are a common part of many winter holiday celebrations. Kids are particularly fascinated by these little bodies of heat and light. And with that fascination comes the inevitable questions: why? and how? 

Why doesn’t the fire get bigger?
Why is there water in the candle?
How does it work?

Not long ago, a winter ice storm came along and knocked out our power. After the initial surprise of being plunged into total darkness, it seemed like the perfect chance for us to investigate just how candles work.

What you need:

  • 8″ piece of cotton string
  • metal butter knife
  • paper towel
  • small dish of water
  • yellow or red food coloring
  • 2 taper candles
  • matches or lighter
Most children have seen a candle burn, but you may wish to have a separate burning candle available for observation during the discussion. Ask your students what burns on a candle.

Does the wick burn?

Tie the piece of cotton string to the handle of a metal butter knife. Light the dangling end of the string and watch it burn up the entire string in a matter of seconds. If the wick were the source of a candle’s fuel, it would not last very long! The wick is not the source of fuel for the candle.

Does the wax burn?

Light a match or use a lighter. Hold the flame beside the solid wax of a candle. The wax will melt and drip, but it will not burn. Wax in its solid or liquid state does not burn.

It’s time to shift gears for a moment. Fill a small dish with water and add a couple drops of food coloring. Tear a paper towel into long narrow strips. Dip one end of a strip of paper towel into the dish and watch the colored water climb up the paper towel. This phenomenon is called wicking or capillary action and is the same thing that happens to the wick of a candle. A candle wick is made of absorbent material just like a paper towel.

When the hot flame from a match or lighter is held to a candle wick, the heat melts some of the candle wax. The liquid wax then travels up the wick by capillary action. When the liquid wax gets close enough to the heat of the flame, it is vaporized or converted to its gaseous state like when water is made into steam. The wax vapor is what burns.

Wax vapor burns

To demonstrate that it is the vaporized wax that is fuel to a candle’s flame light a second candle. Blow out the first candle and quickly move the flame of the second candle into the smoke rising from the extinguished wick of the first candle. Hold it about one inch away and you will see the vapors ignite and relight the wick of the first candle!

Be sure to work on a well-protected surface and wear eye protection, if possible, while using flame and hot wax.

This article was originally published in December 2013 by Home & School Mosaics.

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